Core C will provide purified recombinant wild-type and mutant Surfactant Protein D (SP-D) to PPG investigators in support of their stated aims. Specifically, the Core will provide two general types of proteins: 1) recombinant trimeric neck+CRD (NCRD) fusion proteins or isolated neck+CRD domains of human and rat SP-D expressed in E. coli, and 2) recombinant rat and human SP-D and available mutants of defined oligomeric size expressed by mammalian cells. Both types of proteins will be used by most Projects in the PPG. All proteins are characterized with respect to homogeneity by SDS-PAGE; their non-denatured state of oligomerization, as assessed by gel filtration; carbohydrate binding activity, as assessed by affinity chromatography or solid-phase binding assays; concentration; and the level of endotoxin contamination. If indicated, the mammalian-expressed proteins can be labeled with biotin at the N-linked oligosaccharide at Asn-70, or at primary amino groups, prior to saccharide affinity chromatography and documentation of specific activity. All proteins are tracked from initial expression through storage of the final purified product and shipping. Each protein's life history is documented using an Access database. Although the primary goal is to express proteins using existing cDNAs, we can also assist investigators with the generation of new mutants if indicated by their findings. Thus, the core offers access to highly purified, well-characterized SP-D suitable for a variety of biochemical, biophysical, and biological studies. RELEVANCE (See instructions): Surfactant Protein D (SP-D) is an important mediator of the body's defense against bacteria, viruses and other microorganisms. This Core provides highly purified and well characterized forms of SP-D for the studies described in this Program Project.